Overview

fxrates is a small Go service/library for ingesting exchange rates from pluggable providers and exposing them over HTTP / WS (REST + GraphQL).

What you get

• Runs as a server out of the box: start it and query rates via REST/GraphQL.
• Works as a library: import it and register your own providers, routes, or integrations.
• Configurable storage layer: the storage layer is completely abstracted away, so you can swap implementations without touching ingest/providers. Want to use Mongo, or something else? It should be easy.

Storage implementations

• PostgreSQL (production)
• In-memory (tests / local dev)

Providers

Providers are pluggable fetchers (scrapers, APIs, etc.) scheduled by the ingestor/orchestrator and persisted through the storage interface.

Quick start

Run with Postgres

fxrates serve sql --config ./config.yaml

Run in-memory

fxrates serve memory --config ./config.yaml

REST API

Base path: /v1 All endpoints are read-only.

Common query params

• as_of (optional, RFC3339) - Returns the latest rate at or before this timestamp. Defaults to "now".
• source (optional) - Filter by data source (e.g. BCV, different banks, etc).
• type (optional) - Filter by rate type: MID, BUY, SELL.
• limit (optional) - Page size. Defaults to 100. Clamped to a max (e.g. 500).
• offset (optional) - Number of rows to skip. Defaults to 0.

Data model

Each rate returned looks like:

{
  "as_of": "2026-01-13T04:00:00Z",
  "fetched_at": "2026-01-10T15:43:04Z",
  "base": "USD",
  "target": "VES",
  "rate_type": "MID",
  "source": "BCV",
  "rate": 321.1234
}

Pagination response

Rate endpoints return:

{
  "results": [
    /* exchange rates */
  ],
  "total": 123
}

Errors

Errors are JSON (surprise):

{
  "error": "invalid as_of (must be RFC3339 UTC)"
}

Endpoints

GET /v1/rates/{base}/{target}

Returns rates for a currency pair, as-of a point in time.

If source/type are omitted, you can get multiple results (one per (source, rate_type) bucket). Paginated via limit/offset.

Example:

curl "http://localhost:8080/v1/rates/USD/VES?as_of=2026-01-10T00:00:00Z&limit=100&offset=0"

Filter by source/type:

curl "http://localhost:8080/v1/rates/USD/VES?source=BCV&type=MID"

GET /v1/rates/{base}

Returns rates for a base currency across targets, as-of a point in time.

• If target is not specified (it isn't part of this path), the response can include many targets.
• If source/type are omitted, you can get multiple results per target (one per (source, rate_type) bucket).

Paginated via limit/offset.

Example:

curl "http://localhost:8080/v1/rates/USD?limit=100&offset=0"

Filter:

curl "http://localhost:8080/v1/rates/USD?source=BCV&type=MID"

GET /v1/sources

Lists distinct sources currently present in storage.

Response:

{     
  "results": [
        "BBVA Provincial",
        "BCV",
        "Banco Exterior",
        "Banco Nacional de Crédito BNC",
        "Banco Sofitasa",
        "Otras Instituciones",
        "R4"
    ]
}

Example:

curl "http://localhost:8080/v1/sources"

GET /v1/currencies

Lists distinct currencies currently present in storage.

Response:

{ "results": ["USD", "VES", "EUR"] }

Example:

curl "http://localhost:8080/v1/currencies"

OpenAPI

• Spec: GET /openapi.yaml
• UI: GET /

GraphQL

GraphQL is available at:

• Endpoint: POST /graphql
• Playground: GET /playground

Query: rates

rates mirrors the REST rate endpoints, with optional filters and pagination.

query {
    rates(base: "USD", target: "VES", type: MID, source: "BCV", limit: 10, offset: 0) {
        total
        results {
            as_of
            fetched_at
            base
            target
            rate_type
            source
            rate
        }
    }
}

You can omit target, source, and type to get all matching buckets:

query {
    rates(base: "USD", limit: 50, offset: 0) {
        total
        results {
            target
            source
            rate_type
            rate
            as_of
        }
    }
}

Query: sources / currencies

query {
    sources
    currencies
}